Engineering the directionality of hot carrier tunneling in plasmonic tunneling structures

Abstract

Tunneling metal–insulator–metal (MIM) junctions can exhibit an open-circuit photovoltage (OCPV) response under illumination that may be useful for photodetection. One mechanism for photovoltage generation is hot carrier tunneling, in which photoexcited carriers generate a net photocurrent that must be balanced by a drift current in the open-circuit configuration. We present experiments in electromigrated planar MIM structures, designed with asymmetric plasmonic properties using Au and Pt electrodes. Decay of optically excited local plasmonic modes preferentially creates hot carriers on the Au side of the junction, leading to a clear preferred directionality of the hot electron photocurrent and hence a preferred polarity of the resulting OCPV. In contrast, in an ensemble of symmetric devices constructed from only Au, polarity of the OCPV has no preferred direction.

Chiroplasmonic DNA Scaffolded “Fusilli” Structures

“…Chirality, a key feature of biomolecules, can be transferred into artificial nanomaterials either by producing crystals with chiral shapes or by arranging nonchiral nanocrystals into chiral geometries. − The encoding of structural three-dimensional (3D) information into polymers, where the final shape is dictated by the monomer sequence, showed great promise in this field. , This goal could be achieved by the use of commercially available custom-sequence synthetic DNA and its ability to self-assemble into predetermined geometries in water, following a set of simple hydrogen bond interactions, termed Watson–Crick base-pairing rules. In recent years, this approach sprouted a number of opportunities and challenges, in particular in the fields of nanotechnology and material science. ,− Specifically, due to the large extinction coefficient value associated with their localized plasmon resonance, among other materials, plasmonic nanoparticles (e.g., gold nanoparticles, AuNPs) were the object of extensive experimental efforts to produce materials with designed plasmonic properties − and patterned , or chiroplasmonic geometries. , Several applications of such hybrids were proposed, including their use for imaging mechanical functions of nanoscale machines, ,, their employment as sensors, and their potential application as waveguides …”